I wouldn’t go so far as to say Emperor has absolutely nothing to do with the historical record. Igulden takes some liberties with the history, but at least he tells about what is and isn’t accurate in his historical notes at the end. And as he points out, there isn’t a lot known about Julius Ceaser’s early life. And much less is known about Genghis, but he does stick pretty closely to what little is. What I liked about that series was his ability to present a completely alien mindset; an utterly ruthless conqueror who cared nothing for the traditional prizes of conquest; cities, land, gold, etc. It’s also a very rare thing in history for a single individual to create a nation out of people who never thought of themselves as such. Shaka Zulu did it too, but I can’t think of any others right off.
I’m sorry, making Caesar and Marcus Brutus childhood friends doesn’t even approximate history. There was contemporary gossip that Caesar was Brutus’s father.